Lost circulation shapes

ABSTRACT

Systems and methods for sealing a lost circulation zone associated with a subterranean well include a drill string with a circulating port and a lost circulation material. A lost circulation shape is a hollow body having an outer skin and an open interior chamber. The outer skin includes a plurality of perforations that extend through the outer skin, providing fluid communication between an exterior of the lost circulation shape and the open interior chamber. The plurality of perforations are sized to prohibit a passage of lost circulation material between the exterior of the lost circulation shape and the open interior chamber.

BACKGROUND OF THE DISCLOSURE 1. Field of the Disclosure

The present disclosure relates to subterranean developments, and morespecifically, the disclosure relates to managing lost circulationassociated with a subterranean well.

2. Description of the Related Art

During the drilling of subterranean wells, such as subterranean wellsused in hydrocarbon development operations, drilling mud and otherfluids can be pumped into the well. In certain drilling operations, thewellbore of the subterranean well can pass through a zone that hasinduced or natural fractures, are cavernous, or otherwise have anincreased permeability, which is known as a lost circulation zone. Insuch a case, the drilling mud and other fluids that are pumped into thewell can flow into the lost circulation zone and become irretrievable.

Lost circulation can be encountered during any stage of hydrocarbondevelopment operations. Lost circulation can be identified when drillingfluid that is pumped into the subterranean well returns partially ordoes not return to the surface. While some fluid loss is expected,excessive fluid loss is not desirable from a safety, an economical, oran environmental point of view. Lost circulation can result indifficulties with well control, borehole instability, pipe sticking,unsuccessful production tests, poor hydrocarbon production after wellcompletion, and formation damage due to plugging of pores and porethroats by mud particles. In extreme cases, lost circulation problemsmay force abandonment of a well.

SUMMARY OF THE DISCLOSURE

When unacceptable drilling fluid losses are encountered, conventionallost circulation materials are deployed with the drilling fluid from thesurface. The revised fluid that includes the conventional lostcirculation materials is pumped downhole as part of the standard wellcirculation system. The revised fluid passes through a circulation portto plug and pressure seal the exposed formation at the point wherelosses are occurring. Once sealing has occurred and acceptable fluidloss control is established, drilling operations can resume.Conventional currently available lost circulation material is mosteffective at sealing regularly shaped formation voids with widths up toapproximately 4-6 millimeters (mm). In voids with larger widths,effective sealing is often both challenging and costly.

Embodiments of this disclosure provide a lost circulation shape thatoperates as a complimentary addition to conventional lost circulationmaterial as described in this disclosure. The lost circulation shape canbe deployed with the conventional lost circulation material. The lostcirculation shape is a hollow perforated geometric shape that can fillwith drilling fluid and have a generally neutral buoyancy in thedrilling fluid. Due to this generally neutral buoyancy the lostcirculation shape can move downhole freely with the drilling fluid andexit the drill string through the circulation port with the conventionallost circulation material. The lost circulation shape would be drawninto thief zone cavities or vugulars. The lost circulation shape can actas a trap for the conventional lost circulation material and allow foraccumulation and bridging of the lost circulation material onto the lostcirculation shape. This will result in eventual plugging of theformation.

In an embodiment of this disclosure, a system for sealing a lostcirculation zone associated with a subterranean well includes a lostcirculation material and a lost circulation shape. The lost circulationshape is a hollow body having an outer skin and an open interiorchamber. The outer skin includes a plurality of perforations that extendthrough the outer skin, providing fluid communication between anexterior of the lost circulation shape and the open interior chamber.The plurality of perforations are sized to prohibit a passage of lostcirculation material between the exterior of the lost circulation shapeand the open interior chamber.

In alternate embodiments, the lost circulation shape can have a minimumsize and a maximum size. The minimum size of the lost circulation shapecan be such that a smallest minimum sphere in which the lost circulationshape having the minimum size could fit has a diameter of 5 mm. Themaximum size of the lost circulation shape can be such that a smallestmaximum sphere in which the lost circulation shape having the maximumsize could fit has a diameter of 15 mm. The lost circulation shape caninclude a filling hole, the filling hole extending through the outerskin and having a diameter in a range of 2.5 mm to 5 mm. Filling theopen interior chamber with drilling fluid can include applying a vacuumor applying a pressure to the lost circulation shape before circulatingthe lost circulation material through the drill string.

In other alternate embodiments, the open interior chamber can include adrilling fluid with a drilling fluid density. The lost circulation shapecan have an average lost circulation shape density. A difference betweenthe average lost circulation shape density and the drilling fluiddensity can be 20% or less of the drilling fluid density. Alternately,the difference between the average lost circulation shape density andthe drilling fluid density can be 10% or less of the drilling fluiddensity.

In yet other alternate embodiments, the system can further include acirculating sub and a circulating port that extends through a sidewallof the circulating sub. The lost circulation shape can be sized to flowthrough the circulating sub port with a drilling fluid. The plurality ofperforations can be sized to trap the lost circulation material withinthe lost circulation zone for forming a seal within the lost circulationzone.

In still other alternate embodiments the system can further include adrill string having a circulating port. The drill string can be locatedwithin a wellbore of the subterranean well and defines an annular spacebetween an outer diameter surface of the drill string and an innerdiameter surface of the wellbore. The lost circulation material can belocated within a drilling fluid traveling downhole within the drillstring, through the circulating port, and into the annular space. Thelost circulation shape can be located within the drilling fluidtravelling downhole within the drill string, through the circulatingport, and into the annular space.

In yet another embodiment of this disclosure, a method for sealing alost circulation zone associated with a subterranean well includesproviding a drill string with a circulating port in the subterraneanwell. A lost circulation shape can be circulated through the drillstring. The lost circulation shape can be a hollow body having an outerskin and an open interior chamber. The outer skin includes a pluralityof perforations that extend through the outer skin, providing fluidcommunication between an exterior of the lost circulation shape and theopen interior chamber. The plurality of perforations are sized toprohibit a passage of a lost circulation material between the exteriorof the lost circulation shape and the open interior chamber. The lostcirculation material can be circulated through the drill string.

In other embodiments, the lost circulation shape can be sized to beintroduced into cavities of the lost circulation zone, forming a wedgedlost circulation shape. The method can further include trapping lostcirculation material with the wedged lost circulation shape to seal thelost circulation zone. The lost circulation shape can include a fillinghole that extends through the outer skin and has a diameter in a rangeof 2.5 mm to 5 mm. The method can further include filling the openinterior chamber with drilling fluid that travels through the fillinghole.

In other alternate embodiments, the lost circulation shape can have anaverage lost circulation shape density. A difference between the averagelost circulation shape density and a drilling fluid density can be 20%or less of the drilling fluid density. Alternately, a difference betweenthe average lost circulation shape density and a drilling fluid densitycan be 10% or less of the drilling fluid density. The drill string canfurther include a circulating sub and the circulating port can be acirculating sub port that extends through a sidewall of the circulatingsub. The lost circulation shape can be sized to flow through thecirculating sub port with a drilling fluid.

In yet other alternate embodiments, an annular space can be definedbetween an outer diameter surface of the drill string and an innerdiameter surface of the wellbore. Circulating a lost circulation shapethrough the drill string can include circulating the lost circulationmaterial within a drilling fluid traveling downhole within the drillstring, through the circulating port, and into the annular space.Circulating the lost circulation material through the drill string caninclude circulating the lost circulation shape within the drilling fluidtravelling downhole within the drill string, through the circulatingport, and into the annular space.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features, aspects and advantages of theembodiments of this disclosure, as well as others that will becomeapparent, are attained and can be understood in detail, a moreparticular description of the disclosure may be had by reference to theembodiments that are illustrated in the drawings that form a part ofthis specification. It is to be noted, however, that the appendeddrawings illustrate only certain embodiments of the disclosure and arenot to be considered limiting of the disclosure's scope, for thedisclosure may admit to other equally effective embodiments.

FIG. 1 is a section view of a subterranean well with a drill stringhaving a circulating sub, in accordance with an embodiment of thisdisclosure.

FIG. 2 is a section view of a subterranean well with the drill stringhaving a circulating sub of FIG. 1, shown delivering lost circulationsspheres to a lost circulation zone.

FIGS. 3-4 are perspective views of lost circulation shapes with exampleperforation patterns, in accordance with an embodiment of thisdisclosure.

FIG. 5 is a top view of a lost circulation shape with an exampleperforation pattern and filling hole, in accordance with an embodimentof this disclosure.

FIGS. 6-8 are section views of a lost circulation zone showing theprogression of blocking the lost circulation zone with lost circulationshapes and lost circulation material, in accordance with an embodimentof this disclosure.

FIGS. 9-11 are detailed schematic section views of cavity of a lostcirculation zone showing the progression of blocking the lostcirculation zone with lost circulation shapes and lost circulationmaterial, in accordance with an embodiment of this disclosure.

DETAILED DESCRIPTION

The disclosure refers to particular features, including process ormethod steps. Those of skill in the art understand that the disclosureis not limited to or by the description of embodiments given in thespecification. The subject matter of this disclosure is not restrictedexcept only in the spirit of the specification and appended Claims.

Those of skill in the art also understand that the terminology used fordescribing particular embodiments does not limit the scope or breadth ofthe embodiments of the disclosure. In interpreting the specification andappended Claims, all terms should be interpreted in the broadestpossible manner consistent with the context of each term. All technicaland scientific terms used in the specification and appended Claims havethe same meaning as commonly understood by one of ordinary skill in theart to which this disclosure belongs unless defined otherwise.

As used in the Specification and appended Claims, the singular forms“a”, “an”, and “the” include plural references unless the contextclearly indicates otherwise.

As used, the words “comprise,” “has,” “includes”, and all othergrammatical variations are each intended to have an open, non-limitingmeaning that does not exclude additional elements, components or steps.Embodiments of the present disclosure may suitably “comprise”, “consist”or “consist essentially of” the limiting features disclosed, and may bepracticed in the absence of a limiting feature not disclosed. Forexample, it can be recognized by those skilled in the art that certainsteps can be combined into a single step.

Where a range of values is provided in the Specification or in theappended Claims, it is understood that the interval encompasses eachintervening value between the upper limit and the lower limit as well asthe upper limit and the lower limit. The disclosure encompasses andbounds smaller ranges of the interval subject to any specific exclusionprovided.

Where reference is made in the specification and appended Claims to amethod comprising two or more defined steps, the defined steps can becarried out in any order or simultaneously except where the contextexcludes that possibility.

Looking at FIG. 1, subterranean well 10 can have wellbore 12 thatextends to an earth's surface 14. Subterranean well 10 can be anoffshore well or a land based well, and can be used for producinghydrocarbons from subterranean hydrocarbon reservoirs. Drill string 16can be delivered into and located within wellbore 12. Drill string 16can include tubular member 18 and bottom hole assembly 20. Tubularmember 18 can extend from surface 14 into subterranean well 10. Bottomhole assembly 20 can include, for example, drill collars, stabilizers,reamers, shocks, a bit sub and the drill bit. Drill string 16 can beused to drill wellbore 12. In certain embodiments, tubular member 18 isrotated to rotate the bit to drill wellbore 12.

Wellbore 12 can be drilled through lost circulation zone 22. Inembodiments lost circulation zone 22 is a layer of a subterraneanformation that is located uphole of a hydrocarbon formation, downhole ofa hydrocarbon formation, or between separate hydrocarbon formations. Incertain embodiments, drill string 16 can pass through a cased section ofwellbore 12 of subterranean well 10 in order to reach uncased open holeportion of wellbore 12.

A system for sealing lost circulation zone 22 associated withsubterranean well 10 includes a circulating port to provide downholefluid circulation. The circulating port provides fluid communicationbetween an inner bore of drill string 16 and annular space 26

Annular space 26 is the elongated annular shaped space that extends alength of drill string 16 and is defined between an outer diametersurface of drill string 16 and an inner diameter surface wellbore 12.During downhole fluid circulation, fluids can flow downhole through theinner bore of drill string 16 and uphole through annular space 26. Inreverse circulation, fluids can flow downhole through annular space 26and uphole through the inner bore of drill string 16.

In the example embodiment, drill string 16 can include circulating sub24. Circulating sub 24 can be a circulating sub known and commonlyavailable in the industry for circulating fluids downhole. Circulatingsub 24 can include circulating sub port 28, which is a circulating port.Circulating sub port 28 extends through a sidewall of circulating sub 24and provides fluid communication between the inner bore of drill string16 and annular space 26. In alternate embodiments, bottom hole assembly20 can include the circulating port.

The system for sealing lost circulation zone 22 can be used to seal theentry of cavity 30 of lost circulation zone that has a cross sectionaldimension X up to 25 mm which cannot be sealed with some currentlyavailable lost circulation material. Cavity 30 can be, for example,vugular or cavernous faults. Looking at FIG. 2, after bottom holeassembly 20 has reached or passed through lost circulation zone 22, acombination of lost circulation shape 32 and lost circulation material34 can be used to seal cavities 30 of lost circulation zone 22.

In the example embodiment of FIG. 2, lost circulation shape 32 and lostcirculation material 34 is pumped in a direction downhole through drillstring 16, and exits circulating sub port 28 to reach annular space 26for delivery to lost circulation zone 22.

Looking at FIG. 3, lost circulation shape 32 is a hollow body having anouter skin 36 that defines the shape of lost circulation shape 32 and anopen interior chamber. Outer skin 36 can have a thickness in a range of0.5 mm to 2.5 mm. Lost circulation shape 32 can have a variety ofdiameters. In general, a smaller diameter lost circulation shape 32 canhave a smaller thickness of outer skin 36 and a larger diameter lostcirculation shape 32 can have a larger thickness of outer skin 36. Incertain embodiments, the thickness of outer skin 36 can be directlyproportional to the diameter of lost circulation shape 32. In alternateembodiments, when lost circulation shape 32 has a larger diameter, lostcirculation shape 32 can include an internal support structure, such asa web type structure, to provide internal support to outer skin 36.

In the example embodiments shown, lost circulation shape 32 is a sphere.In alternate embodiments, lost circulation shape 32 can have other threedimensional geometric shapes. As an example, lost circulation shape 32can generally have the shape of a cube, ovoid, egg, hyper rectangle,triangular prism, pyramid, cone, or cylinder.

Lost circulation shape 32 can have a sufficient size to seal lostcirculation zone 22, without being so large in size that lostcirculation shape 32 cannot fit through the circulation port. Lostcirculation shape 32 is sized to flow through the circulation port witha drilling fluid in an unrestricted manner. In certain embodiments, amix of various sizes of lost circulation shapes 32 can be used forsealing cavities 30 of various sizes.

In certain embodiments, lost circulation shape 32 can be formed in avariety of sizes. In certain embodiments, the smallest of lostcirculation shape 32 has a minimum size. The minimum size of lostcirculation shape 32 is such that the smallest minimum hypotheticalsphere in which lost circulation shape 32 having the minimum size couldfit has a diameter of 5 mm, regardless of the geometric shape of lostcirculation shape 32. The largest of lost circulation shape 32 has amaximum size. The maximum size of lost circulation shape 32 is such thata smallest maximum hypothetical sphere in which lost circulation shape32 having the maximum size could fit has a diameter of 15 mm regardlessof the geometric shape of lost circulation shape 32.

Lost circulation shape 32 can be formed of a metal, ceramic, orpolymeric material. As an example, lost circulation shape 32 could beformed of any of a variety of suitable metallic materials, such as, forexample, aluminum, titanium, copper, or nickel. Alternately, lostcirculation shape 32 could be formed of any of a variety of suitableceramic materials, such as, for example, gypsum, alumina, zircon,silicon nitride, glass, or silicate. Alternately, lost circulation shape32 could be formed of any of a variety of suitable polymeric materialsincluding plastic, thermoplastic and elastomers, such as, for example,acrylonitrile butadiene styrene (ABS), high-impact polystyrene (HIPS),polypropylene, polyethylene, nylon, acrylic, polyethylene terephthalate(PET), poly carbonate, or polyurethane.

Alternately, lost circulation shape 32 can be formed of other materialsthat are suitable for additive manufacturing, 3D printing, or otherappropriate fabrication techniques.

The material used to form lost circulation shape 32 can be determined bythe drilling application, the selected drilling fluid, and the lostcirculation material 34 that is to be used for a particular application.In embodiments of this disclosure, lost circulation material 34 and lostcirculation shape 32 can be used to solve a total loss situation wherethere is no need for removal of lost circulation material 34 and lostcirculation shape 32. In other embodiments, lost circulation material 34and lost circulation shape 32 could be formed of a removable material.As an example, lost circulation material 34 and lost circulation shape32 could be formed of aluminum that could be dissolved and removed withan acid treatment.

Outer skin 36 of lost circulation shape 32 includes a plurality ofperforations 38 that extend through outer skin 36. Perforations 38provide fluid communication between an exterior of lost circulationshape 32 and the open interior chamber of lost circulation shape 32.Perforations 38 allow for drilling fluid to enter the open interiorchamber of lost circulation shape 32. Because the drilling fluid canpass into and through lost circulation shape 32, minimal hydrostaticforces are applied to lost circulation shape 32 downhole. Largerperforations 38 will minimize the hydrostatic forces. However, ifperforations 38 are too large, then lost circulation shape 32 will nottrap lost circulation material 34. The size, shape, and number ofperforations 38 can be optimized for each individual application.Alternately, a generic layout of perforations 38 can be developed withthe size, shape, and number of perforations selected to function in avariety of subterranean wells 10.

Perforations 38 are sized to minimize or prohibit the passage of lostcirculation material 34 between the exterior of lost circulation shape32 and the open interior chamber of lost circulation shape 32.Perforations 38 are sized to trap lost circulation material 34 withinlost circulation zone 22, forming a seal within lost circulation zone22. As an example, perforations 38 can have dimensions that are smallerin size than lost circulation material 34 (FIG. 2). Alternately somecommonly available lost circulation material 34 is capable of sealingcavities 30 that have a dimension larger than the size of lostcirculation material 34. In certain embodiments the maximum size ofperforations 38 will be smaller than the maximum bridging limitation oflost circulation material 34. In such embodiments the maximum size ofperforations 38 can be larger than the size of lost circulation material34 so that some lost circulation material 34 pass through perforations38 before lost circulation material 34 bridges across lost circulationshape 32. Performance data can be obtained relating to the capabilitiesof currently available lost circulation material 34. Such performancedata can include the size of cavities that can be sealed with such lostcirculation material. The performance data for a selected lostcirculation material can be referenced for determining a suitable sizeof perforations 38.

In the example of FIG. 3 perforations 38 through outer skin 36 of lostcirculation shape 32 are diamond shaped. In the Example of FIG. 4,perforations 38 through outer skin 36 of lost circulation shape 32 arecircular. When perforations 38 are circular perforations 38 can have,for example, a size in a range of 1 mm to 4 mm in diameter. In alternateembodiments perforations 38 can have other shapes. For example purposesonly, perforations 38 can be shaped as squares, hexagons, pentagons,triangles, rectangles, diamonds, circles or combinations of any of theseshapes. The size, shape, and spacing of perforations 38 can be selectedfor optimized performance with a selected lost circulation material 34(FIG. 2). If the number of perforations 38 is large enough that thestructural integrity of lost circulation shape 32 is compromised, thenstructural members may be added within the open interior chamber of lostcirculation shape 32.

Looking at FIG. 5, lost circulation shape 32 can further include fillinghole 40. Filling hole 40 extends through outer skin 36. In certainembodiments, filling hole 40 can have a diameter in a range of 2.5 mm to5 mm. Filling hole 40 facilitates the filling of the open interiorchamber with drilling fluid. In certain embodiments, the filling of lostcirculation shape 32 could be assisted by holding the lost circulationshape under vacuum and then introducing drilling fluid. Alternately, apressure can be applied instead of a vacuum for filling the openinterior chamber with drilling fluid. Using a vacuum or pressure wouldbe most useful when perforations 38 are sufficiently small that drillingfluid does not travel easily into the open interior chamber. Using avacuum or pressure can overcome surface tension that could prevent theopen interior chamber from filling with drilling fluid before lostcirculation shape 32 is circulated downhole through drill string 16.Filling hole 40 may or may not be a requirement depending on the sizeand arrangement of perforations 38 and the resulting buoyancy of lostcirculation shape 32 in the drilling fluid.

The density of lost circulation shape 32 together with the presence ofdrilling fluid within the open interior chamber of lost circulationshape 32 allow lost circulation shape 32 to have generally neutralbuoyancy within the drilling fluid. As used in this disclosure, agenerally neutral buoyancy means that the lost circulation shapes willflow with the drilling fluid and will not tend to sink or rise relativeto the movement of the drilling fluid.

Because of the drilling fluid located within the open interior chamberof lost circulation shape 32, the average lost circulation shape densitydoes not need to be absolutely equal to the drilling fluid density thatis carrying lost circulation shape 32. The lost circulation shape 32 canbe carried by the drilling fluid free of excessive sinking or rising oflost circulation shape 32 relative to the movement of the drilling fluidif an average lost circulation shape density is near to the density ofthe drilling fluid. As an example, in certain embodiments the differencebetween the average lost circulation shape density and the drillingfluid density is 20% or less of the drilling fluid density. In alternateexample embodiments, the difference between the average lost circulationshape density and the drilling fluid density is 10% or less of thedrilling fluid density.

For the sake of clarity, as an example, a drilling fluid density of somecurrently available drilling fluid can range from 8.0 pounds per gallon(ppg) to 20 ppg. If a drilling fluid with a density of 20 ppg is used,then 20% of 20 ppg is 4 ppg. In this example embodiment, if thedifference between the average lost circulation shape density and thedrilling fluid density is 20% or less of the drilling fluid density,then the average lost circulation shape density can be in a range of 16ppg to 24 ppg.

In embodiments of this disclosure, a mixture of both lost circulationshape 32 and lost circulation material 34 is used to seal lostcirculation zone 22. If some currently available lost circulationmaterial only was used (with no lost circulation shape 32), the lostcirculation material could flow into and out of cavities 30 withoutforming a seal. Some commonly used currently available lost circulationmaterial would be too small relative to the cross sectional dimension Xof cavity 30 for such lost circulation material to effectively anddependably seal lost circulation zone 22. If lost circulations shapes 32were used alone, it is possible that with a sufficient number of lostcirculations shapes 32 that eventually lost circulation zone 22 could besealed. However, because perforations 38 through outer skin 36 couldcontinue to allow for the flow of fluids into and out of the openinterior chamber of lost circulation shapes 32, lost circulation wouldtherefore only be somewhat restricted.

Looking at FIG. 6, lost circulation material 34, and lost circulationshape 32 can be used together and pumped into cavity 30. Looking at FIG.7, by using both lost circulation shape 32 and lost circulation material34, lost circulation shape 32 can be sized to be wedged into cavities 30of lost circulation zone 22, forming a wedged lost circulation shape.With lost circulation shape 32 constrained within lost circulation zone,loss flow will continue through perforations 38. Due to the small sizeof perforations 38, lost circulation material 34 will collect and withinand on the outer surfaces of lost circulation shape 32. Lost circulationmaterial 34 can be trapped by the wedged lost circulation shape to seallost circulation zone 22. Lost circulation material 34 will collect andbridge and cause a total plug and consequent pressure seal. During suchprocess, lost circulation shape 32 may be deformed, collapse, or becrushed due to well bore pressure acting on the formation. Such pressurewill force lost circulation shape 32 and lost circulation material 34further into cavities 30, thereby giving a fully anchored seal. Inalternate embodiments, lost circulation shape 32 may not be deformed,collapse or be crushed, but maintain its original 3-dimensionalstructure.

In an example of operation and looking at FIG. 2, lost circulation shape32 and lost circulation material 34 are circulated downhole throughdrill string 16 with drilling fluid. The drilling fluid can beformulated for the particular conditions of wellbore 12. The drillingfluid can be, for example, a water based mud, an oil based mud, or asynthetic based mud.

Lost circulation shape 32 and lost circulation material 34 can beintroduced into drill string 16 at surface 14 and can exit drill string16 through circulating sub port 28. Because lost circulation shape 32 isgenerally neutrally buoyant in the drilling fluid, the pumping timerequired for delivering lost circulation material 34 to lost circulationzone 22 can be calculated by volume displacement methods, which is wellunderstood in the art of circulating fluids in wellbores.

During the process of delivering lost circulation shape 32 and lostcirculation material 34 downhole, if drilling operations could continuefor a process that used only the lost circulation material 34, thisprocess would not change with the addition of lost circulation shape 32.Therefore, embodiments for delivering the lost circulation shape 32 andlost circulation material 34 downhole could be undertaken while drillingoperations continue and without having to remove drill string 16 fromwellbore 12. The addition of lost circulation shape 32 may not otherwisechange the lost circulation sealing procedure.

Looking at FIGS. 6 and 9, lost circulation shape 32 and lost circulationmaterial 34 enter cavity 30. Looking at FIGS. 7 and 10, lost circulationshape 32 can become wedged within cavity 30. Looking at FIGS. 8 and 11,as drilling fluid continues to pass through lost circulation shape 32,lost circulation material 34 can become lodged in or against lostcirculation shape 32 until a complete formation fault pressure seal isobtained. As lost circulation shape 32 is trapped and lost circulationzone 22 becomes blocked this will result in a pressure differentialcreation across the blockage formed by lost circulation shape 32 due tothe drilling overbalance hydrostatic pressure.

In the example embodiments of FIGS. 8 and 11, lost circulation shape 32has deformed, collapsed or been crushed within cavity 30. A crushed lostcirculation shape 32 could potentially trap lost circulation materialmore quickly than uncrushed lost circulation shape 32. In addition, acrushed lost circulation shape 32 could potentially become lodged deeperinto cavity 30, providing a more secure seal of lost circulation zone 22(FIG. 1).

Lost circulation shape 32 is sized to be wedged into cavities 30 of lostcirculation zone 22, forming a wedged lost circulation shape. Lostcirculation material 34 is then trapped by the wedged lost circulationshape to seal lost circulation zone 22.

Embodiments described in this disclosure therefore provide systems andmethods that are capable of sealing a lost circulation zone withcavities that are larger than those that can be sealed with currentlyavailable lost circulation material. Systems and methods provide fordelivery to the lost circulation zone 22 without the need for a specificsecondary remedial bottom hole assembly or the need for a longer,adapted, or revised sealing operation.

Embodiments of this disclosure, therefore, are well adapted to carry outthe objects and attain the ends and advantages mentioned, as well asothers that are inherent. While embodiments of the disclosure has beengiven for purposes of disclosure, numerous changes exist in the detailsof procedures for accomplishing the desired results. These and othersimilar modifications will readily suggest themselves to those skilledin the art, and are intended to be encompassed within the spirit of thepresent disclosure and the scope of the appended claims.

What is claimed is:
 1. A system for sealing a lost circulation zoneassociated with a subterranean well, the system including: a lostcirculation material; and a lost circulation shape, the lost circulationshape being a hollow body having an outer skin and an open interiorchamber, where the outer skin includes a plurality of perforations thatextend through the outer skin, providing fluid communication between anexterior of the lost circulation shape and the open interior chamber,the plurality of perforations sized to prohibit a passage of lostcirculation material between the exterior of the lost circulation shapeand the open interior chamber.
 2. The system of claim 1, where the lostcirculation shape has a minimum size and a maximum size, where: theminimum size of the lost circulation shape is such that a smallestminimum sphere in which the lost circulation shape having the minimumsize could fit has a diameter of 5 mm; and the maximum size of the lostcirculation shape is such that a smallest maximum sphere in which thelost circulation shape having the maximum size could fit has a diameterof 15 mm.
 3. The system of claim 1, where the lost circulation shapeinclude a filling hole, the filling hole extending through the outerskin and having a diameter in a range of 2.5 mm to 5 mm.
 4. The systemof claim 1, where the open interior chamber includes a drilling fluidwith a drilling fluid density and the lost circulation shape has anaverage lost circulation shape density, and where a difference betweenthe average lost circulation shape density and the drilling fluiddensity is 20% or less of the drilling fluid density.
 5. The system ofclaim 1, where the open interior chamber includes a drilling fluid witha drilling fluid density and the lost circulation shape has an averagelost circulation shape density, and where a difference between theaverage lost circulation shape density and the drilling fluid density is10% or less of the drilling fluid density.
 6. The system of claim 1,further including a circulating sub and a circulating port that extendsthrough a sidewall of the circulating sub, and the lost circulationshape is sized to flow through the circulating port with a drillingfluid.
 7. The system of claim 1, where the plurality of perforations aresized to trap the lost circulation material within the lost circulationzone for forming a seal within the lost circulation zone.
 8. The systemof claim 1, the system further including a drill string having acirculating port, the drill string being located within a wellbore ofthe subterranean well and defining an annular space between an outerdiameter surface of the drill string and an inner diameter surface ofthe wellbore.
 9. The system of claim 8, where: the lost circulationmaterial is located within a drilling fluid traveling downhole withinthe drill string, through the circulating port, and into the annularspace; and the lost circulation shape is located within the drillingfluid travelling downhole within the drill string, through thecirculating port, and into the annular space.
 10. A method for sealing alost circulation zone associated with a subterranean well, the methodincluding: providing a drill string with a circulating port in thesubterranean well; circulating a lost circulation shape through thedrill string, the lost circulation shape being a hollow body having anouter skin and an open interior chamber, where the outer skin includes aplurality of perforations that extend through the outer skin, providingfluid communication between an exterior of the lost circulation shapeand the open interior chamber, the plurality of perforations sized toprohibit a passage of a lost circulation material between the exteriorof the lost circulation shape and the open interior chamber; andcirculating the lost circulation material through the drill string. 11.The method of claim 10, where the lost circulation shape is sized to beintroduced into cavities of the lost circulation zone, forming a wedgedlost circulation shape.
 12. The method of claim 11, further includingtrapping lost circulation material with the wedged lost circulationshape to seal the lost circulation zone.
 13. The method of claim 10,where the lost circulation shape includes a filling hole extendingthrough the outer skin and having a diameter in a range of 2.5 mm to 5mm, and the method further includes filling the open interior chamberwith drilling fluid that travels through the filling hole.
 14. Themethod of claim 13, where filling the open interior chamber withdrilling fluid includes applying a vacuum to the lost circulation shapebefore circulating the lost circulation material through the drillstring.
 15. The method of claim 13, where filling the open interiorchamber with drilling fluid includes applying a pressure to the lostcirculation shape before circulating the lost circulation materialthrough the drill string.
 16. The method of claim 10, where the lostcirculation shape has an average lost circulation shape density, andwhere a difference between the average lost circulation shape densityand a drilling fluid density is 20% or less of the drilling fluiddensity.
 17. The method of claim 10, where the lost circulation shapehas an average lost circulation shape density, and where a differencebetween the average lost circulation shape density and a drilling fluiddensity is 10% or less of the drilling fluid density.
 18. The method ofclaim 10, where the drill string further includes a circulating sub andthe circulating port is a circulating sub port that extends through asidewall of the circulating sub, and the lost circulation shape is sizedto flow through the circulating sub port with a drilling fluid.
 19. Themethod of claim 10, where an annular space is defined between an outerdiameter surface of the drill string and an inner diameter surface of awellbore, and where: circulating the lost circulation shape through thedrill string includes circulating the lost circulation material within adrilling fluid traveling downhole within the drill string, through thecirculating port, and into the annular space; and circulating the lostcirculation material through the drill string includes circulating thelost circulation shape within the drilling fluid travelling downholewithin the drill string, through the circulating port, and into theannular space.